Turning on the light system also turns prims with the keywordspanel to full bright, for control panels or decorative purposes.

The lights can be set to turn on/off automatically with the vehicle by enabling the AutoLights feature from the vehicle menu.

If you need the headlight switch to activate something else, like a sound or particle routine, you can customize the full permission LightSystem script included in the Additional Scripts box, and place that in any prim in the build.